Jaime, I just use a grill over the top of my container pond. You can see pictures here. For what it's worth, I've noticed that these shrimp do get a bit paler than the ones I leave inside. I always assumed it was the difference in diet, but it could be environmental.

See, I've always heard the colors are much more vibrant when they are kept outdoors probably due to the light. Hmmmmm. Something for my to think about. I've only had them out there a few weeks and they are juvies so it's hard to tell much of anything right now. DOesn't help I can't see into the container too good either. LOL! Did you ever have issues with drangonfly or damselfly nymphs getting in there? That's my main concern.